Combined power supply and scanning generator system



H. M. LEWIS 2,300,452

COMBINED POWER-SUPPLY AND SCANNING GENERATOR SYSTEM Filed Oct. 18, 1940 2 Sheets-Sheet 2 INVENTOR HAROLD M. LEWIS FIG. 4.

C INTERMEDIATE- FREQUENCY AMPLIFIER ATTORNEY Patented Nov. 3, 1942 co map rowan sums sun some cam-mason srs'rm Harold M. Lewis, Great Neck, N.

Haleltine Corporation, a corporation ware Y., assignor to of Dela- Application October 18, mo, set-n1 No. 861,700 7.

Claims. (01. 250-27) The present invention relates to an improved power-supply and scanning generator system for a cathode-ray tube television signal-translating system and, particularly, to a power-supply and scanning generator system adapted simultaneously to provide a plurality of output potentials, one of which is a periodic potential of saw-tooth wave form and another of which is a substantially steady high 7 unidirectional potential. While the invention is oi general application, it has particular utility as a power-supply system for supplying the energizing potential and one scanning potential to an electrostatic deflection type of cathode-ray image-reproducing tube used in television receivers and the invention will, therefore, be described in this connection.

Present day television receivers conventionally use a cathode-ray tube type oi image reproducer which requires scanning currents or potentials of saw-tooth wave form for its deflecting'electrodes and a substantially steady unidirectional potential of relatively high voltage, 01! the order of 5,000 to 10,000 volts, for energization of one or more of the anodes with which it is provided.

A local oscillator or generator of saw-tooth potentials is conventionally used as the source of scanning potentials in television carrier-signal receivers including electrostatic deflection type cathode-ray tubes. The substantially steady high voltage energizing potentials have heretoiore generally been obtained by transforming the relatively low voltage oi the alternating current power-supply mains to the required high voltage which is then rectified and suitably filtered. The conventional prior art arrangements for generating scanning potentials have been incapable of supplying high voltage energizing potentials and, conversely, the source of high voltage has not been able directly to supply the scanning potentials. Consequently, the carrier-signal television receivers oi the prior art have required independent sources 01 scanning and energizing potentials which undesirably increases the complexity and expense of the receiver. The use of the alternating current power mains as a source of high voltage supply has the disadvantages that it necessitates a relatively large and expensive transformer and filter unit and creates an excessive danger of electrical shock, due to the large storage of energy in the relatively large filter condensers required for suitably filtering out the components of the low frequency generally employed in commercial power-supply systems. I I

It has heretofore been proposed that generatore of saw-tooth scanning current be also used as a source of high voltage energizing potentials by suitable rectification and filtering of a periodic voltage derived from the scanning currents. Great care must be taken in the design of generators oi! saw-tooth current to maintain linearity of the wave form of the current. Generators of this nature, therefore, involve a relatively expensive construction and cannot readily be designed in a form suitable to deliver the desired high unidirectional output potential without impairing the linearity of the saw-tooth current wave.

It is an object oi the invention. therefore. to

provide an improved, simplified, and economical power-supply system which, while of general application, isparticularly suited for use in a carrier-signal television receiver and one which avoids one or more of the above-mentioned disadvantages and limitations of the prior art devices,

. It is a further object of the invention to provide a power-supply system wherein a potential of saw-tooth wave form and a substantially steady high unidirectional potential are simultaneously derived from a single generator of periodic voltage of pulse wave form. The sawtooth potential circuit may, if desired, be balanced with respect to ground: that is, it may comprise terminals at which the amplitudes of the saw-tooth potentials vary equally above and below ground potential.

In accordance with the invention, a combined power-supply and scanning generator system for a cathode-ray tube television signal-translating system comprises a relaxation oscillator for generating a periodic voltage, a rectifier device and an impedance network coupled to the oscillator to develop across the network a unidirectional potential. The network includes two portions having unequal time constants, the time constant of one of the network portions being so proportioned that the one portion provides a source of periodic potential of saw-tooth wave form and the time constant of the other of the network portions being so proportioned that the otherportion provides a source of substantially steady high unidirectional potential. The system additionally includes a cathode-ray tube defiection circuit coupled to one of the portions of the impedance network to utilize the periodic potential of saw-tooth wave form and a cathoderay tube space current path coupled to the other of the network portions to utilize the substantially steady high unidrectional potential.

For a better understanding of the Present invention, together with other and further objects thereof, reference is had to the following description taken in connection with the accompanying drawings, and its scope will be pointed out in the appended claims.

Referring now to the drawings, Fig. 1 is a circult diagram, partly schematic, of acomplete carrier-signal television receiver embodying V the invention; Fig. 2 comprises graphs representing current and voltage variations occurring at cer-- tain points of the arrangement of Fig. 1, and is used as an aid in explaining the operation of the invention; and Figs. 3 and 4 are circuit diagrams representing modified forms of the invention.

Referring now more particularly to Fig. 1. there is represented schematically a complete carriersignal television receiver of a conventional design embodying the present invention in a preferred form. In general, the receiver includes a radiofrequency amplifier l having its input circuit connected to an antenna system ii, iii, and having its output circuit connected to an oscillatormodulator l3. Connected in cascade with theoscillator-modulator l3, in the order named, are an intermediate-frequency amplifier ll of one or more stages, a detector and automatic amplification control system ill, a video-frequency amplifier it of one or more stages, and an image reproducer I! of the electrostatic deflection cathode-ray tube type. Also connected to the output of unit I5 is a synchronizing-signal separator l8 to the output of which are coupled a field-scanning system l8 and a combined powersupply and scanning generator system 20, more fully described hereinafter, comprising a source of line-scanning potentials and a source of steady high unidirectional voltage for the first and second anodes of image reproducer ll.

An automatic amplification control or A. V. C. circuit is connected between the output circuit of the A. V. C. supply of unit It and the input circuits of one or more of the tubes of the radiofrequency amplifier Hi, the oscillator-modulator l3, and the intermediate-frequency amplifier It in conventional manner.

Sound-signal translating and reproducing apparatus 9 is also connected to the output of the oscillator-modulator l3 and may include, connected in cascade in the order named, one or more stages of intermediate-frequency amplification, a detector, one or more stages of audio-frequency amplification, and a sound-reproducing device.

It will be understood that the various units just described may, with the exception of the powersupply system 20, be of a conventional construction and operation, the details of which are well known in the art, rendering detailed description thereof unnecessary. Considering briefly the operation of the television receiver as a whole, and neglecting for the moment the operation of the power-supply system 20 presently to be de-' scribed, a desired image-modulated carrier signal is selected and amplified by the radio-frequency amplifier l0, converted to an image-modulated intermediate-frequency carrier signal in the oscillator-modulator l3, amplified in the intermediate-frequency amplifier l4, and detected by the detector ofunit l5, thereby to derive the video-frequency and synchronizing-signal modulation components. The video-frequency components are, in turn, amplified in. the video-frequency amplifier i6 and are applied to the input electrodes of the image reproducer IT to modulate the cathode-ray beam thereof. The synchronizsignal are separated from the video-frequency.

components by the synchronizing-signal separator I8, and the field-synchronizing and line-syn- 5 chron and applied, respectively, to the fiel system I8 and to the power-supply system 20. The field-scanning system It applies a scanning I potential of saw-tooth wave form to the field- 10 "S anning electrodes of image reproducer I! while "--"the power-supply system applies a line-scanning potential of saw-tooth wave form to the linescanning electrodes of image reproducer ll, thereby to deflect the cathode-ray beam of image reproducer H in two'directions normal to each other, visually to reproduce the received television image. The power-supply system 20 additionally and simultaneously supplies the, steady high unidirectional voltage required by the first and second anodes of the image reproducer ll.

' The automatic amplification control or A. V. C. bias derived from the A. V. C. supply of unit I 5 is effective to control the amplification of one or more of the units l0, l3, and I to maintain the signal input to the detector 01' unit I! within a relatively narrow range for a wide range of received signal intensities.

The sound-signal modulated-carrier wave accompanying the desired vision-signal modulatedcarrier wave is also intercepted by the antenna system H, l2, selected and amplified in the radiofrequency amplifier l0, and applied to the oscillator-modulator l3, wherein it is converted to an intermediate-frequency signal and applied to the input of the sound-signal translating apparatus 8. Here the sound-signal modulated intermediate-frequency carrier signal is, in turn, amplified, detected to derive the modulation components which are further amplified, and reproduced by the sound-reproducing device of the apparatus 9. I

Referring now more particularly to the portion of the system embodying the present invention, the combined power-supply and scanning generator system 20 includes a relaxation oscillator 2i of the E/L type for generating a periodic voltage, such as disclosed in the United States Letters Patent No. 2,118,977, granted May 31, 1938, to Harold M. Lewis and Madison Cawein, and as- 60 signed to the same assignee as the present application. The oscillator 2| includes a tube 2la, a transformer 22 having anode and grid windings 23, 24, respectively, coupled to provide feedback between the anode and grid of tube 2la, the windings 23 and 24 having a minimum capacitance in shunt therewith. The choice of the oscillator circuit constants should be such as to provide normal operation at a frequency somewhat lower than the frequency of the line-synchronizing signal applied to the input circuit of the oscillator from the synchronizing-signal separator l8, whereby synchronism may readily be effected by the synchronizing signal.

The transformer 22 has a secondary winding 25 across the terminals of which are serially connecteda diode rectifier device 26 and a rectifier load circuit comprising an impedance network 21. The impedance network 21 includes a first portion 28 having a relatively short time cond-scanning long time constant, the network portions 28. and 29 being coupled in parallel with each other through an isolating impedance, preferably a resistor 30 of high ohmic value. The network portion 28 comprises a resistor 3| and shunt-conizing signals are separated from each other stant and a second portion 29 having a relatively c 7 2,800,452 nected condenser 82 while the second network portion 29 similarly comprises serially-arranged resistors 33 and 84 across the terminals of which is connected a condenser 35. Coupledto the first network portion 28 is a cathode-ray tube deilection circuit comprising the input circuit of a balanced line-frequency scanning-potential amplifier 38. 36, the output circuit of which is coupled to the line-scanning electrodes of the image reproducer II. There are coupled to the second network portion 29 a plurality of space current paths comprising first and second anodeenergizing circuits 3'! and 38. respectively, oi image reproducer i1 and an anode-energizing circuit 39 of the balanced amplifier 36, 36.

7 In considering the operation of the circuit just described. it will be assumed that a line-irequency synchronizing signal oi pulse wave form is applied ,i'rom the synchronizing-signal separator it to the input circuit of oscillator tube 2 in with the pulses negatively poled. The means ror applying synchronizing pulses from the synchronizing-signal separator it to the tube Zia, therefore, constitutes a means for synchronizing the oscillator 2! with the received signal. The

oscillator tube tic normally is conductive during the trace portion of each scanning cycle and the negative pulses are of sumcient amplitude to render it nonconductive during each retrace portion. Thus. the oscillator generates a periodic current of exponential or approximately"sawtooth wave form represented by curve A of Fig. 2. From this current, there is developed across all windings oi transformer 2i, and particularly across the secondary winding it, a periodic voltage of modified rectangular-pulse wave form as represented by curve B of Fig. 2. There is a high voltage step-up ratio between the primary and secondary windings oi transformer 22,

whereby the amplitude of the positive pulses of this periodic voltage in the secondary winding 2G is oi the order oi several thousand volts, for

larity that the positive half-cycles are rectified to develop across the network til a high unidirectional potential.

The time constant of the network portion 23 is so proportioned that this network portion provides a source of periodic potential of saw-tooth wave form. That is, the proportioning is such that the unidirectional potential developed across the portion 23 has a wave form represented by curve C of Fig. 2 and contains a periodic potential component e oi saw-tooth wave form and an average unidirectional potential component E of arelatively high value of the order of several thousand volts. The component of saw-tooth wave form e, which is synchronous with the line-synchronizing signals applied to oscillator ii, is applied through a blocking condenser to the input circuit of the push-pull linefrequency scanning amplifier 35, 38 where it is amplified and applied to the line-scanning electrodes of the image reproducer H.

The second network portion 29 and the isolating resistor to are so proportioned that the second network portion provides a source of substantially stead-y high unidirectional potential.

Thus, the proportioning of the network portion 29 is such that the saw-tooth component of the unidirectional voltage developed across the first network portion 28 is filtered out, whereby there is developed across the network portion 29 the potential component E. This potential is applied through the space current paths 81. 88 to energize image reproducer i1 and is additionally applied through the space current path 39 to energize the amplifier 88, 36.

A modified form of the power-supply system of the invention is represented by the circuit diagram of Fig. 3 which is essentially similar to the arrangement of Fig. 1, similar circuit elements being designated by similar reference characters, the principal difierence being that the resistor 3| of impedance network 21 is grounded at its center point rather than, at one end, whereby the impedance elements of the first network portion 28 are balanced with respect to 1 ground. This permits the connection of the lineone-half of the average unidirectional potential substantially steady high unidirectional average E developed across the network portion 28 is available to produce the high unidirectional voltage developed across the second network portion 29. The detailed operation of this modified form of the invention will, therefore. not be repeated.

While it has been-stated that the line-synchro nizing component of the synchronizing signal is applied to the power-supply system 20 to derive therefrom a line-scanning potential of saw-tooth wave form, it will be evident that the circuit constants of oscillator 2| may be so chosen that the oscillator operates at field-scanning frequency, the oscillator being then synchronized by the field-synchronizing signal and its output sawtooth potential being applied to the field-scannin electrodes of image reproducer ii. In this event, the scanning system It would become the linescanning system and would be of any suitable conventional type. However, there is an advantage in utilizing the power-supply system 20 to generate line-scanning potentials in that the constants of the impedance network 2? may then be materially smaller due to the higher frequency of the line-scanning potentials, and there consequently is a decrease in the cost of the cirthe full average unidirectional potential E developed across the network portion 28 is available for energizing the cathode-ray tube.- A second isolating impedance, preferably a resistor 38a of high ohmic value, couples one terminal of the network portions 28 and 29, the resistor coupling the opposite terminals as in the preceding modifications. Resistors 33 and 36 have equal values of resistance and the junction of the resisters is grounded. Condensers 40 and M of equal values of capacitance are connected across the respective resistors 33 and 34. the second network portion 29 comprising, in this modification. the resistors 33, 34 and the condensers 40, M. The network 21 therefore consists of two network portions 28 and 29, the impedances of each of which are balanced with respect to ground. In this modification, also, the cathode of cathoderay tube i1 is connected to an ungrounded terminal of network portion 29 rather than directly to ground, as in the circuit oi Fig. 8.

The operation of this modified form. of the invention is essentially similar to that oi Fig. 3. Since the cathode and second anode of tube ii are connected to opposite terminals of the second network portion 29, it is evident that the full average unidirectional potential Eis available for application to these two elements.

From the foregoing description of the invention, it will be apparent that a power-supply systern embodying the invention has the advantage that it requires only a relatively simple and inexpensive oscillator and provides simultaneously a source of periodic voltage of saw-tooth wave form and a source of steady high unidirectional voltage. The power-supply system of the invention has the additional advantage that the loading thereof by the space currents oi the several space current paths coupled thereto does not aimed in the appended claims to cover all such changes and modifications asfall within the true spirit and scope of the invention.

What is claimed is: 1. In a cathode-ray tube television signaltranslating system, a combined power-supply and scanning generator system comprisin arelaxation oscillator for generating a periodic voltage. a rectifier device and an impedance network coupled to said oscillator to develop across said network a unidirectional potential, said network including two portions having unequal time constants, the time constant of one of said network portions being so proportioned that said one portion provides a source of periodic potential of I saw-tooth wave form and thetime constant oi the other of said network portions being so proportioned that said other portion provides a source otsubstantially steady high unidirectional potential, a cathode-ray tube deflection circuit coupled to said one of said portions of said network to utilize said periodic potential of sawtooth wave iorm,.and a cathode-ray tube space current path coupled to said other of said network portions to utilize said substantially steady high unidirectional potential.

-2. In a cathode-ray tube television signal translating system, a combined power-sup ly and -.scanning generator system comprising, a relaxation oscillator for generating a periodic voltage. a rectifier device and an impedance network coupled to said oscillator to develop across said network a unidirectional potential, said network including two portions in parallel with one another and having unequal time constants. the time constant of one of said network portions being so proportioned that said one portion provides a source or periodic potential of saw-tooth wave form and .the time constant oi the other of said network portions being so proportioned that said other portion provides a source oi substantially steady high unidirectional potential, a cathode-ray tube deflection circuit coupled to said one of said portions of said network to utilize said periodic potential of saw-tooth wave form, and a cathode-ray tube space current path coupled to said other of said'network portions to utilize said substantially steady high unidirectional' potential.

translating system, a combined power-supply and scanning generator system comprising, a relaxation oscillator for generating a periodic voltage. a rectifier device and an impedance network coupled to said oscillator to develop across said network a unidirectional potential, said impedance network comprising a resistive-capacitive network including two portions having unequal time constants, the time constant of one of said network portions being so proportioned that said one portion provides a source oi periodic potential of saw-tooth wave form and the time constant oi the other oi said'network portions being so proportioned that said other portion provides a source 01 substantially steady high unidirectional potential, a cathode-ray tube deflection circuit coupled to said one of said portions of said network to utilize said periodic potential of saw-tooth wave form, and a cathode-ray-tube space current path coupled to said other of said network portions to. utilize said substantially steady highvunidlrectional potential.

4. In a cathode-ray tube television signaltranslating system, a combined power-supply and to scanning generator system comprising, a relaxation oscillator for generating a mriodic voltage. a rectifier device and an impedance network cupled to said oscillator to develop across said network a unidirectional potential, said impedance 85 network having a first portion or relatively short time constant and a second portion of relatively long time constant, an isolating impedance interposed between said network portions, the time constant of said first network portion being so proportioned that said first portion provides a source 01' periodic potential 01' saw-tooth wave form andithe time constant of said second network portion being so proportioned that said second portion provides a source .or substantially steady high unidirectional potential, a cathoderay tube deflection circuit coupled to said one 01' a said portions 01' said network to utilize said periodic potential or saw-tooth wave form, and a cathode-ray tube space current path coupled to 60 said other of said network portions to utilize said substantially steady high unidirectional potential.

5. In a cathode-ray tube television signaltranslating system, a combined power-supply and scanning generator system comprising, a relaxation oscillator for generating a periodic voltage of pulse wave form, a rectifier device and an impedance network coupledto said oscillator to develop across said networkza unidirectional potential. said network including two portions having unequal time constants, the time constant of one of said network portions being so proportioned that said one portion provides a source of periodic potential of saw-tooth wave form and the time constant of the other or said network portions being so proportioned that said other portion provides a source or substantially steady high unidirectional potential, a cathode-ray tube deflection circuit coupled to said one 01' said portions 01' said network to utilize said periodic potential or saw-tooth wave form. and a cathoderay tube space current path coupled to said other or said network portions to utilize said substantially steady high unidirectional potential. 6. In a cathode-ray tube television signaltranslating system, a combined power-supply and -s. m a cathode-ray tube television signalscanning generator system comprising, a relaxation oscillator for generating a periodic voltage of wave form having a pulse component, a rectifier device and an impedanc network coupled to said oscillator to develop across said network a unidirectional potential, said network including two portions having unequal time constants, the tim constant of one of said network portions being so proportioned that said one portion provides a source of periodic potential of saw-tooth wave form and the time constant of the other of said network portions being so proportioned that said other portion provides a source of substantially steady high unidirectional potential, a cathode-ray tube deflection circuit coupled to said one of said portions of said network to utilize utilize said substantially steady high unidirectional potential.

7. In a cathode-ray tube television signaltranslating system, a combined power-supply and scanning generator system comprising, an oscillator having a circuit in which is developed a periodic current of approximately saw-tooth wave form, a rectifier device and an impedance network including two portions having unequal time constants, means for deriving from said periodic current a periodic voltage of wave form having a pulse component and for applying said derived voltage to said rectifier device and said impedance network to develop across said network a unidirectional potential, the time constant of one or said network portions being so proportioned that said on portion provides a source of periodic potential of saw-tooth wave form and the time constant of the other of said network portions being so proportioned that said other portion provides a source of substantially steady high unidirectional potential, a cathode-ray tube deflection circuit coupled to said one of said portions of said network to utilize said periodic potential of saw-tooth waveform, and a cathoderay tube space current path coupled to said other of said network portions to utilize said substantially steady high unidirectional potential.

anced with respect to ground, the time constant of said one network portion being so proporv 'tioned that said one portion provides a source of balanced periodic potential of saw-tooth wave form and the time constant of the second of said network portions being so proportioned that said second portion provides a source of substantially steady high unidirectional potential, a cathoderay tube deflection circuit coupled to said one of said portions of said network to utilize said periodic potential of saw-tooth wave form, and a cathode-ray tube space current path coupled to said other of said network portions to utilize said substantially steady high unidirectional potential.

9. In a cathode-ray tube television signaltranslating system, a combined power-supply and scanning generator system comprising, means for generating a periodic voltage, a rectifier device and an impedance network coupled to said means to develop across said network, a unidirectional potential, said network including two portions the impedances of each of which are balanced with respect to ground, the time constant of said one network portion behig so proportioned that said one portion provides a source of balanced periodic potential of saw-tooth wave form and the time constant of the second of said network portions being so proportioned that said second portion provides a source of substantially steady high unidirectional potential. a cathode-ray tube deflection circuit coupled to said one of said portions oi said network to utilize said periodicpotential of saw-tooth wave form, and a cathoderay tube space current path coupled to said other or said network portions to utilize said substantially steady high unidirectional potential.

10. In a cathode-ray tube television signaltranslating system, a combined power-supply and scanning generator system comprising, a relaxation oscillator for generating a periodic voltage, means for synchronizing said oscillator with a received signal, a rectifier device and an impedance network coupled to said oscillator to develop across said network a unidirectional potential, said network including two portions having unequal time constants, the time constant of one of said network portions being so proportioned that said one portion provides a source of periodic potential 01 saw-tooth wave form and the time constant of the other of said network portions being so proportioned that said other portion provides a source of substantially steady high unidirectionalpotential, a cathode-ray tube deflection circuit coupled to said one of said portions of said network to utilize said periodic potential of saw-tooth wave form, and a cathoderay tube space current path coupled to said other of said network portions to utilize said substantially steady high unidirectional potential.

HAROLD M. LEWIS. 

